The present invention relates to electric meters containing electronic registers and, more particularly, to a physical construction of electronic registers adapted for efficient integration with their electric meters.
Conventional electric meters employ an aluminum disk driven as a rotor of a small induction motor by an electric field at a speed proportional to the electric power being consumed by a load. Geared dials, or cyclometer discs, integrate the disk motion to indicate the total energy consumed, conventionally measured in kilowatt hours (one kilowatt hour equals one thousand watts of power consumption for one hour).
In addition to the above measurement of consumption, some electric meters contain means for separating the consumption into portions occurring during predetermined peak and off-peak hours, and means for recording maximum demand during those predetermined periods of time in order to adjust billing according to such parameters. In one such demand register disclosed in U.S. Pat. No. 3,586,974, a mechanical demand register records the power usage during a predetermined period of time, and stores that value for later reading. The predetermined period of time may be, for example, the time between meter readings, or a period of time corresponding to a billing period of the utility providing the power. A clockwork mechanism restarts the demand register at the ends of regular demand intervals of, for example, a fraction of an hour so that, at the end of the predetermined period, the stored value represents the highest value of power usage occurring during any one of the regular demand intervals in the predetermined period.
Mechanical registers, such as disclosed in the referenced U.S. patent, have limited flexibility. The design of a particular meter is not transferable to another meter having a different physical configuration. In addition, the measurement functions of a particular register cannot be redefined without major mechanical redesign. Greater flexibility may be obtained using electronic acquisition, integration and processing of power usage. An electronic processor such as, for example, a microprocessor, may be employed to manage the acquisition, storage, processing and display of usage and demand data. U.S. Pat. Nos. 4,179,654; 4,197,582; 4,229,795; 4,283,772; 4,301,508; 4,361,872 and 4,368,519, among others, illustrate the flexibility that electronic processing brings to the power and energy usage measurements. Each of these electronic measurement devices includes means for producing an electronic signal having a characteristic such as a frequency or a pulse repetition rate, related to the rate of power usage. The electronic processor is substituted for the mechanical register of the prior art to keep track of the power usage during defined periods of time.
Various aspects of an electronic register which may benefit from the techniques of the present invention are disclosed in U.S. patent application Ser. Nos. 599,684; 599,685; 599,736; 599,744; 599,683; 599,735; 599,743 and 599,742, all filed on Apr. 12, 1984; and Ser. Nos. 550,407 and 550,142 both filed on Nov. 10, 1983, the disclosures of which are herein incorporated by reference. For present purposes, it is sufficient to state that, since the electronic register is called on to perform many functions, it necessarily requires the inclusion of a large number of parts when compared to the number of parts in the electro-mechanical portion of the electric meter. As a consequence, it can be anticipated that an electronic register of an electric meter may require field service more often than the remainder of the electric meter. Thus, a desirable characteristic of an electronic register is ease of troubleshooting and service.
A favored technique for field service on an electronic register includes substitution of a known-good electronic register for one that is apparently in a failed condition. In order to avoid the need to reprogram the programmed constants for a particular application, and to avoid losing stored billing data, a method was disclosed in the referenced patent applications for copying the contents from a non-volatile storage in one electronic register to a non-volatile storage in another electronic register which may then be substituted for the original electronic register. The above-referenced patent applications also disclose apparatus and method for storing necessary data in non-volatile storage in the event of a power outage or entry into a test mode. Since such apparatus and methods are fully disclosed in the referenced patent applications they need not be repeated here.
Since substitution is expected in field service, it is important that an electronic register provides means for ensuring secure connection to the remainder of the register.